If you have an HD4xxx series card, Catalyst 12.4 is the newest driver to support it (as of June 4, 2012). This won't work with X version 1.12 (the one packaged with Fedora 17). To downgrade to X version 1.11, use the following commands (as root). Note: I'm assuming x86_64IMPORTANT: I'd highly recommend going down to runlevel 3 first. You can do this using the following command in one of the text consoles (<CTRL> + <ALT> + <Fx> where x is 1-9, just try them until you get to a console)

systemctl isolate runlevel3.target

Commands for downgrading X:

yum erase xorg-x11-drv-intel

yum --releasever=16 install libxcb* xcb-util startup-notification*

yum --releasever=16 downgrade *xcb* xorg*

You may also need libxcb.i686 from the Fedora 16 release. The intel driver has additional dependencies, and those with AMD/ATi cards don't need it anyway.

UPDATE
3.4.0 has been pushed as the most recent kernel update. This will require recompiling the drivers in addition to commenting the two lines out of uaccess_64.h. Make sure you've rebooted into the new kernel before compiling the driver. To compile go to the directory where the amd-driver-installer-12-4-x86.x86_64.run file is and type:

./amd-driver-installer-12-4-x86.x86_64.run --extract fglrx

You will then need to edit ./fglrx/common/lib/modules/fglrx/build_mod/kcl_ioctl.c and add the line

DEFINE_PER_CPU(unsigned long, old_rsp);

on line 220 directly under the end of the multi-line comment. You also need to edit line 4157 of ./fglrx/common/lib/modules/fglrx/build_mod/firegl_public.c to be

for_each_possible_cpu(p)

.
After this, execute

./fglrx/common/lib/modules/fglrx/build_mod/make.sh

as root. If you get an error about no make target for libfglrx_ip.a, then copy the one from ./fglrx/arch/x86_64/lib/modules/fglrx/build_mod to ./fglrx/common/lib/modules/fglrx/build_mod/ and try again.
Finally, run

./fglrx/common/lib/modules/fglrx/make_install.sh

as root then

reboot

to check your results, which I do by seeing if this command correctly outputs a temperature.